/* Demos textures receding into the distance and stretched in foreground.
   Use the 'r' key to reveal the underlying quads.

Scott D. Anderson
scott.anderson@acm.org
Fall 2003
*/

#include <stdio.h>
#include <math.h>                /* for sqrt */
#include <tw.h>

/* ================================================================
   code for the grass
*/

/* This unit square is on the XZ (y=0) plane, in the ++ quadrant. */

bool reveal = false;

void drawUnitSquare(int w, int h ) {
    int i,j;
    GLfloat dw = 1.0/w;
    GLfloat dh = 1.0/h;
    glNormal3f(0,1,0);
    for( i=0; i<w; ++i) {
        glBegin( reveal ? GL_POINTS : GL_TRIANGLE_STRIP );
        for( j=0; j<=h; ++j ) {
            if(j%2) glTexCoord2f(1,0); else glTexCoord2f(0,0);
            glVertex3f(dw*i,     0, dh*j);
            if(j%2) glTexCoord2f(1,1); else glTexCoord2f(0,1);
            glVertex3f(dw*(i+1), 0, dh*j);
        }
        glEnd();
    }
}

bool color = false;

const int NUM_TEXTURES = 3;

GLuint textureIDs[NUM_TEXTURES];
int TextureNumber = 0;

void draw_grass() {
    /*draw texture*/
    if(color) {
        glColor3f(0, .7, 0);
        glDisable(GL_TEXTURE_2D);
    } else {
        glBindTexture(GL_TEXTURE_2D, textureIDs[TextureNumber]);
        glEnable(GL_TEXTURE_2D);
    }
    glPushMatrix();
    glTranslatef(-100, 0, 0);
    glScalef(200, 1, 100);
    drawUnitSquare(20, 2);    // this supplies texture coordinates
    glPopMatrix();
}

void init() {
    glGenTextures(NUM_TEXTURES,textureIDs); /* get all the texture ids */
    twLoadTexture(textureIDs[0],"grass.ppm");
    twLoadTexture(textureIDs[1],"brick.ppm");
    twLoadTexture(textureIDs[2],"wood-laminate.ppm");
}

/* ================================================================
   Call backs
*/

void display(void) {
    twDisplayInit();
    twCamera();
    glPushAttrib(GL_ALL_ATTRIB_BITS);
    
    draw_grass();  

    /*draw sky on the XY plane */
    glDisable(GL_TEXTURE_2D);
    glColor3f(.7, .9, 1);
    glBegin(GL_POLYGON);
    glVertex3f(-200, 0, 0);
    glVertex3f(+200, 0, 0);
    glVertex3f(+200, 200, 0);
    glVertex3f(-200, 200, 0);
    glEnd();

    glPopAttrib();
    glutSwapBuffers();
    glFlush();
}

void key(unsigned char k, int xx, int yy) {
    switch(k) {
    case 'r': reveal = !reveal; break;
    case 'c': color = !color; break;
    case '0': 
    case '1': 
    case '2': TextureNumber = k-'0'; break;
    }
    glutPostRedisplay();
}

int main(int argc, char** argv) {
    glutInit(&argc,argv);
    glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH );
    twInitWindowSize(500,500);
    glutCreateWindow(argv[0]);
    glutDisplayFunc(display);
    init();
    twBoundingBox(-50,+50,0,50,0,20); // lies, all lies
    twMainInit();
    twKeyCallback('r',key,"toggle reveal quads");
    twKeyCallback('c',key,"toggle color");
    twKeyCallback('0',key,"texture 0");
    twKeyCallback('1',key,"texture 1");
    twKeyCallback('2',key,"texture 2");
    glPointSize(3);             // big dots when revealing the quads
    glutMainLoop();
    return 0;
}